I thought this list would be helpful to some people. =)
Credit: http://sonic.wikia.com/wiki/List_of_games
Sonic the Hedgehog (16-bit) (1991)
Sonic the Hedgehog (8-bit) (1991)
Sonic Eraser (1991)
SegaSonic Cosmo Fighter (1991)
Waku Waku Sonic Patrol Car (1991)
Sonic the Hedgehog 2 (8-bit) (1992)
Sonic the Hedgehog 2 (16-bit) (1992)
Sonic Spinball (1993)
Dr. Robotnik's Mean Bean Machine (1993)
SegaSonic the Hedgehog (1993)
Sonic CD (1993)
Sonic Chaos (1993)
Sonic the Hedgehog 3 (1994)
Sonic Triple Trouble (1994)
Sonic & Knuckles (1994)
Wacky Worlds Creativity Studio (1994)
Sonic Gameworld (1994)
Tails and the Music Maker (1994)
Sonic Drift (1994)
Knuckles' Chaotix (1995)
Sonic Drift 2 (1995)
Tails' Skypatrol (1995)
Tails Adventure (1995)
Sonic Labyrinth (1995)
Sonic Compilation (1995)
Sonic Blast (1996)
Sonic's Schoolhouse (1996)
Sonic 3D (1996)
Sonic the Fighters (1996)
Sonic R (1997)
Sonic & Knuckles Collection (1997)
Sonic Jam (1997)
Sonic Adventure (1998)
Sonic the Hedgehog Pocket Adventure (1999)
Sonic Shuffle (2000)
Sonic Adventure 2 (2001)
Sonic Advance (2001)
Sonic Adventure 2: Battle (2001 JAP) (2002 NA)
Sonic Mega Collection (2002)
Sonic Advance 2 (2002)
Sonic Pinball Party (2003)
Sonic Adventure DX: Director's Cut (2003)
Sonic Battle (2003 JAP) (2004 NA)
Sonic Heroes (2003 JAP) (2004 NA)
Sonic Advance 3 (2004)
Sega Superstars (2004)
Sonic Mega Collection Plus (2004)
Sonic Gems Collection (2005)
Shadow the Hedgehog (2005)
Sonic Rush (2005)
Sonic Riders (2006)
Sonic the Hedgehog (2006)
Sonic the Hedgehog Genesis (2006)
Sonic Rivals (2006)
Sonic and the Secret Rings (2007)
Sonic Rush Adventure (2007)
Sonic X (Leapster) (2007)
Mario and Sonic at the Olympic Games (2007)
Sonic Rivals 2 (2007)
Sonic Riders: Zero Gravity (2008)
Super Smash Bros. Brawl (2008)
Sega Superstars Tennis (2008)
Sonic Chronicles: The Dark Brotherhood (2008)
Sonic Unleashed (2008)
Sonic's Ultimate Genesis Collection (2009)
Sonic and the Black Knight (2009)
Mario and Sonic at the Olympic Winter Games (2009)
Sonic & Sega All-Stars Racing (2010)
Sonic Classic Collection (2010)
Sonic the Hedgehog 4: Episode I (2010)
Sonic Free Riders (2010)
Sonic Colors (2010)
Sonic Generations (2011)
Mario & Sonic at the London 2012 Olympic Games (2011)
Sonic the Hedgehog 4: Episode II (2012)
Credit: http://sonic.wikia.com/wiki/List_of_games
Sonic the Hedgehog (16-bit) (1991)
Sonic the Hedgehog (8-bit) (1991)
Sonic Eraser (1991)
SegaSonic Cosmo Fighter (1991)
Waku Waku Sonic Patrol Car (1991)
Sonic the Hedgehog 2 (8-bit) (1992)
Sonic the Hedgehog 2 (16-bit) (1992)
Sonic Spinball (1993)
Dr. Robotnik's Mean Bean Machine (1993)
SegaSonic the Hedgehog (1993)
Sonic CD (1993)
Sonic Chaos (1993)
Sonic the Hedgehog 3 (1994)
Sonic Triple Trouble (1994)
Sonic & Knuckles (1994)
Wacky Worlds Creativity Studio (1994)
Sonic Gameworld (1994)
Tails and the Music Maker (1994)
Sonic Drift (1994)
Knuckles' Chaotix (1995)
Sonic Drift 2 (1995)
Tails' Skypatrol (1995)
Tails Adventure (1995)
Sonic Labyrinth (1995)
Sonic Compilation (1995)
Sonic Blast (1996)
Sonic's Schoolhouse (1996)
Sonic 3D (1996)
Sonic the Fighters (1996)
Sonic R (1997)
Sonic & Knuckles Collection (1997)
Sonic Jam (1997)
Sonic Adventure (1998)
Sonic the Hedgehog Pocket Adventure (1999)
Sonic Shuffle (2000)
Sonic Adventure 2 (2001)
Sonic Advance (2001)
Sonic Adventure 2: Battle (2001 JAP) (2002 NA)
Sonic Mega Collection (2002)
Sonic Advance 2 (2002)
Sonic Pinball Party (2003)
Sonic Adventure DX: Director's Cut (2003)
Sonic Battle (2003 JAP) (2004 NA)
Sonic Heroes (2003 JAP) (2004 NA)
Sonic Advance 3 (2004)
Sega Superstars (2004)
Sonic Mega Collection Plus (2004)
Sonic Gems Collection (2005)
Shadow the Hedgehog (2005)
Sonic Rush (2005)
Sonic Riders (2006)
Sonic the Hedgehog (2006)
Sonic the Hedgehog Genesis (2006)
Sonic Rivals (2006)
Sonic and the Secret Rings (2007)
Sonic Rush Adventure (2007)
Sonic X (Leapster) (2007)
Mario and Sonic at the Olympic Games (2007)
Sonic Rivals 2 (2007)
Sonic Riders: Zero Gravity (2008)
Super Smash Bros. Brawl (2008)
Sega Superstars Tennis (2008)
Sonic Chronicles: The Dark Brotherhood (2008)
Sonic Unleashed (2008)
Sonic's Ultimate Genesis Collection (2009)
Sonic and the Black Knight (2009)
Mario and Sonic at the Olympic Winter Games (2009)
Sonic & Sega All-Stars Racing (2010)
Sonic Classic Collection (2010)
Sonic the Hedgehog 4: Episode I (2010)
Sonic Free Riders (2010)
Sonic Colors (2010)
Sonic Generations (2011)
Mario & Sonic at the London 2012 Olympic Games (2011)
Sonic the Hedgehog 4: Episode II (2012)